CONDENSATION AND EVAPORATION OF INTERSTELLAR CLOUDS IN CHEMODYNAMICALMODELS OF GALAXIES

The network of interactions between hot gas, cool clouds, massive star s, and stellar remnants used in the chemodynamical modeling of the int erstellar medium is investigated for the types of its solutions. In a physically consistent formulation for the energy transfer during conde nsation, oscillations due to a cyclic switching between condensation a nd evaporation never occur. A closed-box system evolves in a hierarchy of equilibria: thermal balance in the cloud gas, star-formation self- regulated due to heating of the clouds by massive stars, and the balan ce of condensation and evaporation. Except for an initial transitory p hase, the evolution of the metallicity follows that of the Simple Mode l quite closely. For galaxies with a high initial density, or if the c ondensation rate is low, the metals produced by the stars may remain s tored in the hot gas phase even in evolved systems with low gas fracti ons.